I. Field
The present invention relates generally to communication, and more specifically to techniques for performing data detection for a hierarchical coded data transmission in a wireless communication system.
II. Background
Hierarchical coding is a data transmission technique whereby multiple (e.g., two) data streams are superimposed (e.g., added) together and transmitted simultaneously. The “coding” in this context refers to channel coding rather than data coding at a transmitter. Hierarchical coding may be advantageously used, for example, to deliver broadcast services to users within a designated broadcast area. These users may experience different channel conditions and achieve different signal-to-noise-and-interference ratios (SNRs). Consequently, these users are capable of receiving data at different data rates. With hierarchical coding, broadcast data may be divided into a “base stream” and an “enhancement stream”. The base stream is processed and transmitted in a manner such that all users in the broadcast area can recover the stream. The enhancement stream is processed and transmitted in a manner such that users with better channel conditions can recover the stream.
To recover a hierarchical coded data transmission, a receiver first detects and recovers the base stream by treating the enhancement stream as noise. The receiver then estimates and cancels the interference due to the base stream. The receiver thereafter detects and recovers the enhancement stream with the interference from the base stream canceled. For improved performance, the base stream and enhancement stream are typically recovered sequentially, one stream at a time, in the order described above. Large amount of processing is typically required to recover each stream. Moreover, large amount of buffering may also be required, depending on the manner and speed in which each stream can be detected and recovered. The large amounts of processing and buffering may impact system performance and cost.
There is therefore a need in the art for techniques to efficiently perform data detection for a hierarchical coded data transmission.